1. Field of the Invention
The invention relates to liquid crystal display (LCD) technology, and in particular to a pixel structure for a transflective LCD device to improve pixel reliability, and a method for fabricating an LCD device with the improved pixel structure.
2. Description of the Related Art
Liquid crystal display (LCD) devices are widely used in electronic devices such as portable computers, PDAs and cell phones. Typically, LCD devices are classified into transmissive and reflective types. The former utilizes a backlight as the light source and the latter utilizes ambient light. The transmissive LCD device exhibits a high contrast ratio and good color saturation. However, it is difficult to decrease power consumption due to power requirements of the backlight. Reflective LCD devices have the advantage of power-saving under bright ambient light. However, their contrast ratio is lower and color saturation inferior to transmission types. Moreover, the reflective LCD device is limited showing images under dark ambient conditions.
In order to improve the drawbacks of these two types of LCD device, a transflective LCD device has been developed, displaying in transmissive and reflective modes. FIG. 1 illustrates a conventional transflective LCD device. The device includes a lower substrate 100 (referred to as an array substrate), an upper substrate 114 and a liquid crystal layer 108 disposed therebetween. The lower substrate 100 comprises a pixel region (consisting of a reflective region R and a transmissive region T) defined by a pair of scan lines (not shown) and a pair of data lines (not shown). A thin film transistor (not shown) is disposed on the lower substrate 100 of the reflective region R and electrically connected to the scan line and the data line. A protective layer 102 and a pixel electrode are successively disposed on the lower substrate 100. The pixel electrode includes a transparent electrode 104 and an overlying reflective electrode 106. The reflective electrode 106 is disposed in the reflective region R to partially overlap the transparent electrode 104. A color filter (CF) 112 and a transparent dielectric layer 110 are successively disposed on the upper substrate 114. The transparent dielectric layer 110 formed on the color filter 112 (also referred to as step on CF (SOC) structure) corresponds to the reflective region R to form a transflective LCD device with dual cell gap.
In the transflective LCD device with dual cell gap, however, peeling of the transparent electrode 104 near the edge of the transmissive region T may occur during defining the overlying reflective layer for formation of reflective electrode 106, as shown in FIG. 2, reducing the pixel reliability. The transparent electrode 104 has worse adhesion strength at the edges of the pixel region due to the step height produced by the underlying scan line and data line, resulting in stress concentration. In particular, after lithography on the reflective layer for formation of the reflective electrode, the photoresist, the reflective layer and the transparent electrode in the transmissive region may peel off the protective layer.
Thus, there exists a need in the art for development of an improved pixel structure which can prevent the transparent electrode from peeling to improve pixel reliability.